Realized heritabilities were estimated for the character of phenthoate resistance in two local strains of the diamond‐back moth, Plutella xylostella L. (Lepidoptera: Yponomeutidae), by performing artificial laboratory selection for resistance and susceptibility to phenthoate. Heritability estimates indicated that such traits are moderately heritable (ĥ2 = 0.42 and 0.41 in the resistant selection and ĥ2 = 0.31 and 0.21 in the susceptible selection), and give an experimental basis accounting for rapid evolutionary changes of phenthoate resistance observed in field populations of this insect.
The observed changes in variances of phenthoate susceptibility are discussed in relation to the additive genetic variance eliminated by directional selection. The explanation stresses the importance on the underlying genetic system.
Résumé
Calcul de l'héritabilité de la résistance de Plutella xylostella au phenthoate
L'héritabilité de la résistance au phenthoate obtenue chez deux souches locales de P. xylostella L. (Lep.; Yponomeutidae) a été calculée en procédant au laboratoire à des sélections artificielles pour la résistance et pour la sensibilité à cet insecticide. Les calculs de l'héritabilité ont montré que de tels caractères sont moyennement héritables (ĥ2 = 0,42 et 0,41 lors de la sélection pour la résistance, et ĥ2 = 0,31 et 0,21 lors de la sélection pour la sensibilité), et ont fourni la base expérimentale rendant compte des changements évolutifs rapides observés pour la résistance au phenthoate chez des populations naturelles de cet insecte.
Les changements observés de la variance de la sensibilité au phenthoate sont discutés en fonction de la variance génétique additive éliminée par la sélection orientée. L'explication insiste sur l'importance du système génétique souligné.
As the first step to clarify the mechanism of insecticide resistance, the susceptibility of 4 strains of the diamondback moth against 4 organophosphorus and 2 carbamate insecticides, cartap and fenvalerate were assessed by the topical application method. The results showed that the resistant strains were highly resistant to 3 organophosphorus compounds (phenthoate, prothiophos and cyanophos), moderately to 2 carbamate insecticides (acephate and methomyl) and cartap, but no obvious resistance was observed for dichlorvos and fenvalerate.
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